The study investigated the relationship between Self-concept and Academic Performance in Mathematics of Senior High School Students. The respondents of this study are the 119 senior high school students of Sugod Senior High School, Sugod Bacon District Sorsogon City. Data were collected using a 30-item self-concept questionnaire checklist adopted from the study of Peteros (2012). Their academic performances were assessed using their average rating in General Mathematics for the 1st Semester, S.Y. 2020-2021. The collected data were treated using percentage, weighted mean, Chi-square, and t-test statistics, tested at a 0.05 level of significance. Students have varying levels of self-concept along learned, organized, and dynamic which are described as moderate. Most of the students got an overall level of performance that is described as satisfactory with moderate self-concepts. The self-concept of the students along learned, organized, and dynamic are significantly related to each other. It was suggested that teachers should develop their student’s positive self-concept toward Mathematics and establish a pleasant teaching experience to enhance higher self-concept and better performance in mathematics.